The present invention relates to a method and apparatus for scrubbing flue gas that is charged with noxious material, with the scrubbing being accomplished via flowable absorbing material in a gas-scrubbing unit having an atomizing device with at least one independent nozzle in which, pursuant to the gas-spraying or air flow atomization principle, the absorbing material, as atomizing material, is atomized in parallel flow with a gas, as an atomizing medium, to form a fine droplet stream while at the same time the atomizing material and the atomizing medium are intensely mixed.
Methods and apparatus are known for atomizing additive suspensions, in the form of flowable absorbing material, in flue gas scrubbing units. These methods and apparatus are based on various atomizing methods depending upon the type of scrubbing unit.
Thus, for example, atomizers operating pursuant to the "rotary-disk" principle are known for flue gas scrubbing units which are designed as spray-absorption-dryers. These atomizers essentially comprise a high speed disk that receives atomizing material. Due to the resulting centrifugal forces, the atomizing material is flung over the edge of the disk, which produces a hollow conical stream of drops. The flue gas and the additive suspension are supplied to the reactor at different locations. An optimum mixing of the two streams cannot be achieved under these conditions. The flue gas that flows by it also causes atomizing material to cake onto the disk since the flue gas reacts with the additive suspension on that side of the disk that is not directly supplied, and/or because reaction products are transported to such locations. This caking action adversely affects the quality of the atomization. Another drawback to this heretofore known atomizer is the equipment itself, which includes rotating structural elements and the mechanical stresses associated therewith.
Flue gas scrubbing units utilizing the wetwash process frequently operate with pressure spray guns or atomizers. With such atomizers, the additive suspension is supplied to the atomizer nozzle at high pressure. In several embodiments, the flow of the additive suspension into the nozzle is swirled, with the additive suspension being atomized as it exits due to the forces resulting from the drop in pressure. Compared to other atomizing systems, the pressure atomizers produce drops having a relatively large diameter. However, a particular drawback of such pressure atomizers is that the required atomization quality is provided only at design pressure, so that relatively poorer results are produced at partial load operation. These drawbacks are not eliminated by undertaking various modifications of the pressure atomizer. For example, a nozzle has been used that due to the relatively large inner volume of the nozzle and the large outlet opening thereof effects an acceleration of the atomizing material already in the nozzle. Swirling the stream produces a relatively wide hollow conical stream of drops at the outlet of the nozzle. However, the previously mentioned drawbacks relative to an inadequate mixing between the additive and the flue gas are still present.
It is therefore an object of the present invention to provide, in flue gas scrubbing units which are designed to operate pursuant to either spray absorption or the wet wash process, a high quality atomization of the additive suspension accompanied by simultaneous intensive mixing with the flue gas, even for partial load operation, without having the process be adversely affected by additive being caked on in or to the atomizer.